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Black Gap Elves

My three-year adventure with the smallest owl in North America.

By Bonnie McKinney

The elves were due back this week. I had been patiently waiting for days. Each evening, as dusk approached and the sun's last rays slanted across the desert flats, I walked the area around the Black Gap Wildlife Management Area headquarters checking for the elves. They usually arrived from March 15-17 each year, and for years they had been on time. The elves had a long journey with many hazards along the way before reaching the Black Gap, in West Texas.

Perhaps they were already here, hiding in the vegetation, but I had not heard a single peep from them. I continued my walk around headquarters, stopping and listening in the early evening darkness. A common poorwill called and another answered, then all was quiet. Resigned to the fact that this was March 17 and they were not back, I headed to the house. Suddenly, a sharp, puppy-like yip erupted, shattering the desert stillness, then another, and yet another - yes, they were back and on time.

Elf owls are the smallest owls in North America, and one of the smallest in the world. They are migrants, spending the winter in the Mexican states of Michoacan, Morelos, Guerrero, Puebla, Oaxaca and part of Sinaloa. Early spring finds the elf owl migrating back to their breeding grounds in west and south Texas, parts of California, New Mexico and Arizona. In Mexico, they breed in the states of Coahuila, Nuevo Leon, Baja Sur, Sonora, Puebla and Guanajuato.

In Texas, elf owls are unevenly distributed from the south Texas brush country to the Rio Grande Valley. In West Texas, they are found in the Trans-Pecos region in the scattered mountains in pine-oak woodland habitat, the lower desert elevations and along the Rio Grande riparian corridor, eastward to Val Verde County.

I had observed elf owls at Black Gap for many years and in 1994 began a three-year study on this tiny owl. Their arrival in March 1994 was eagerly anticipated because I wanted to determine if elf owls would use nest boxes. Why? The elf owl is a cavity-nesting species, and in the lower desert elevations of West Texas, trees are scarce. Elf owls use old abandoned cavities of ladder-backed woodpeckers in the lower desert habitat. The woodpeckers excavate cavities in the trunks of yucca, stalks of maguey plants, fence posts, dead tree limbs and electric poles. I had noticed that a number of power poles were being downed and the lines were being placed underground. If significant numbers of these poles were removed, both the ladder-backed woodpecker and the elf owl populations could be impacted by the absence of cavity-nest sites. The Black Gap had a very healthy population of elf owls and was the perfect location to test the nest boxes, since my husband, Billy Pat, and I had lived at Black Gap since 1981 and were both employed by the Texas Parks and Wildlife Department. My proposed study was approved; I had a small budget and a lot of enthusiasm. I designed a nest box, purchased the lumber and hardware needed for construction, and cajoled our son, Matt, into volunteering his time to help me build 80 nest boxes. The boxes were up, placed in different habitats from the low desert to the higher arid canyons, and along the Rio Grande corridor. I was anticipating the elf owls finding their new deluxe accommodations and providing me detailed insight into the natural history of a little-known species in West Texas. If the elf owls used the nest boxes, the information could be shared with area landowners wishing to provide habitat enhancement for elf owls, especially if power poles were being removed from their lands.

The male elf owls were back, evidenced by the three calling at the Black Gap headquarters. Males always arrive first and begin calling at dusk, advertising their presence to other males and establishing their small territories and checking available nest sites. The females arrive seven to 10 days later than the males.

In the ensuing days, I checked the three males around the headquarters every night; watched them hunt for moths, and, yes, the male with the territory in our yard went in and out of the nest box several times. However, he also visited the old ladder-backed woodpecker nest site higher up on the same power pole. Would he pick the woodpecker nest site or the new deluxe accommodations in the nest box? Time would tell, and the final choice would be up to the female.

The females arrived during the night of March 26, eight days after the males. The next evening at dusk, the desert was alive with the puppy-like continuous yips of the males calling to the females. All I needed was a flashlight, a comfortable seat in the yard and my notebook. Amid much fanfare of flying back and forth, entering the nest box and then leaving, the male was trying his best to entice the female to his choice of a nest site. This continued for several nights, and finally the female flew close to the box. The male's excited yips increased in volume to a frantic pitch, and his tiny round face with white eyebrows was framed in the entrance hole to the nest box. The female perched at the entrance hole, the male slowly descended into the bottom of the nest box, his yips changing to softer churr sounds; the female answered with a high-pitched phew vocalization. This courtship behavior continued for hours, slowing around 3 a.m., then resuming from 5 a.m. to daylight. Both then flew into an ash tree and were immediately concealed in the leafy vegetation. Once the pair bond between the male and female is established, the female begins day roosting in the nest site, and the male starts bringing her food. As egg laying and incubation nears, she spends more time in the nest cavity, flying at dusk and dawn to stretch her wings.

While making the rounds, I noticed that if female elf owls were roosting inside when I approached the boxes, they would fly from the box, then re-enter as soon as I left the immediate area. A total of 19 boxes had female elf owls day roosting. That was great news, but I purposely stayed away from the boxes for several days in order to decrease any disturbance I might be creating. I didn't want the females to abandon the nest boxes. After waiting almost a week I decided that egg laying was well underway. Early the next morning, I quietly placed a ladder against the power pole in our yard and climbed up to the nest box. Slowly, I opened the hinged top, and to my surprise and delight, I was face-to-face with a tiny elf owl female that was stretched as high as her five-inch height would allow. Her gray-brown feathers were puffed up, beak snapping – 48 grams of mad momma elf owl. I gently moved her to the side of the box and saw that she was incubating three white eggs.

I needed to take a series of measurements, weigh and photograph her, as well as band her with a United States Fish and Wildlife aluminum band and a tiny color band to make her identification easy without having to recapture her. I gently picked her up, only to have her lie flat on her back in the palm of my hand. Amazingly, she offered no resistance and did not try to escape, but remained perfectly still, glaring at me with those fierce yellow eyes. I quickly recorded the necessary data and replaced her in the nest box.

I headed for the field to check the rest of the nest boxes. No females were leaving the boxes, which meant they were sitting tight on eggs. I began a long day of banding, measuring, weighing, counting eggs and marveling at the gentle nature of these tiny owls. Elf owls lay from one to five white eggs; the normal clutch is two to three eggs. The eggs are not laid all at once, but at intervals over a several-day period, thus when the eggs hatch, the tiny owls are different sizes. The female performs all the incubation duties, with the male making many nightly trips to and from the nest site with food for the female.

Now that egg laying was over, and incubation well underway, I needed information on their diet; what prey did they find in their small territories? In the low desert country, elf owl prey consisted of moths, occasionally a small black-headed snake, crickets, centipedes, beetles and scorpions.

Incubation lasts around 24 days. Once the eggs hatch, the young fledge from 28 to 32 days later, looking much like carbon copies of the adults.

Before the young fledged, I documented nesting success and banded, weighed and measured the young owlets. The first year of the study, the occupancy rate was very good, and the rate continued to increase year after year. Many of the banded females returned to the same nest boxes, or to nearby boxes. During the second and third year of the study, many of the nestlings I banded returned to their natal areas as adults to raise their young.

Elf owls have adapted to habitats from pine-oak woodlands to the low desert. They require cover, cavity nest sites and an abundant insect supply. In the lower desert elevations, nest boxes can enhance habitat for elf owls, particularly if power poles have been removed or if natural nest sites are not abundant.

Threats to elf owls are loss of habitat along riparian corridors, development of desert country for urban and agricultural purposes, and loss of structures for cavity nests. In the low desert, the natural predator of the elf owl is the great horned owl, which preys on adults and fledglings. Ringtails are suspected of breaking and eating eggs.

If you live in West Texas, particularly in the low desert country, take time to listen for the desert elves. They are easy to identify - their tiny size, round head, white eyebrows, grayish-brown feathers and yellow eyes are distinct field marks. Their calls are diagnostic - a loud, puppy-like "yipping." If you decide to install nest boxes to enhance their habitat, please don't disturb the nesting owls. They will tolerate your presence from a distance and provide many hours of enjoyment.

During my three-year study of the Black Gap elf owls, I developed a deeper understanding of their natural history, the dangers they face, their ability to adapt to various habitats, and their incredible homing instinct to return yearly to the same area to nest and raise their young.